The invention pertains to devices used for manual transmission motor vehicles, to allow the operator to start up the vehicle while it is parked on an incline, without having the vehicle begin to roll downhill before the operator can begin a controlled acceleration. With a conventional manual transmission vehicle, the operator must, when starting up from a parked position, push down on the clutch pedal with one foot, shift into gear, and push down on the accelerator pedal with the other foot. The clutch pedal foot must be kept on the clutch pedal during shifting into first gear, and into higher gears. Since the other foot must be kept on the accelerator during the initial acceleration when getting underway from a parked position, the operator does not have a foot free to operate the brake pedal. This causes a problem when starting up from a parking position on a hill or other incline. Even if the hand brake had been engaged when the vehicle was parked, the operator must release it to start up. Since the operator does not have a foot free to operate the brake pedal during the initial gear shifting and acceleration, the vehicle will tend to roll downhill, out of control, before the operator can begin a safe, controlled acceleration. So there is a need for a mechanism whereby the operator can apply braking action without having to use the brake pedal, during the start up phase of operation.
Although various other means have previously been devised to accomplish this purpose, including the provision of mechanical linkage devices between the clutch pedal and the brake pedal, as in U.S. Pat. No. 4,538,710 of Taig, the present invention provides a more advantageous mechanism, involving a combination clutch and brake master cylinder (in addition to the conventional brake master cylinder), and a linkage mechanism connecting the clutch pedal to this combined clutch--brake cylinder, whereby the operator, in order to apply the brakes, need only further depress the clutch pedal, after having depressed it sufficiently to disengage the clutch.
The present invention also deals with other problems which are encountered in the operation of a conventional manual transmission vehicle. After the operator has already completed the initial acceleration of the vehicle, frequent up or down gear shifting is necessary as the vehicle is driven in city traffic, due to frequently changing speeds of other vehicles. If another motorist or a pedestrian suddenly pulls out in front of the operator, while the operator is engaged in gear shifting, an accident may result from the extra time required for the operator to put a foot onto the brake pedal, before the brake pedal can be depressed. But with the present invention, since the operator's foot is already on the clutch pedal, and since braking power may be applied by simply further depressing the clutch pedal, without moving a foot from one pedal to another, there is a better chance to avoid such an accident.
The present invention is also relevant to two problems arising in starting and operation of a manual transmission vehicle in cold weather conditions. Without the present invention, when starting a vehicle in cold weather on a slanted home driveway, if the emergency brake doesn't function well to prevent the vehicle from rolling backwards (as some do not), it will be necessary to shift the transmission into neutral, and use the left foot on the brake pedal, while using the right foot on the accelerator to rev and warm the engine. In this situation the starter is turning the engine with thickened, cold oil, and is also turning the main transmission gear. But with the present invention the operator can disengage the clutch and engage the brake with the same clutch pedal. In this way the starter is only turning the engine, so that there is less load on the starter and the battery, and the engine will crank more rapidly to high RPM, and start more easily.
The invention also deals with a cold weather operation problem which frequently occurs in the first few minutes of operation, when the vehicle is stopped at a traffic light on an upward incline, and the engine tends to stop because it hasn't been sufficiently warmed. Without the present invention, it is again necessary to shift into neutral, and use one foot on the brake pedal, to keep the vehicle from rolling backwards, while keeping the other foot on the accelerator. When the light turns green, and the operator depresses the clutch pedal to put the transmission in gear, with the transmission gear rapidly rotating from the engine having been "revved" while waiting at the red light, there is a resulting tendency for "grinding" as the transmission is forced into gear. Although many operators manage to avoid this problem by "riding" the clutch, or partially engaging the clutch just sufficiently to keep the vehicle from rolling backwards without using the brake pedal, this method is unsatisfactory because it causes premature wear of the clutch disc. With the present invention this problem also can be avoided, through use of the same pedal to control both the clutch and braking action.